After being out of town for a few days, I was finally able to get board to the board and add a decoupling cap:

Ugly, but it works!

I tried putting a little super glue down to hold it in place, but that didn’t harden fast enough and ultimately caused more problems than it was worth. Despite what it looks like, I did use some actual wire (actually spare leads cut off from some through hole parts) in addition to the solder. It’s ugly, but it does actually solve my problem! No more spurious interrupts! Now I cat get my entire binary pattern displayed!

I still have my 1 ms delay in there from my testing to see if that fixes the interrupt problem, so that’s why the pattern stays constant around the magnet. But the rest of it looks great! Now I can finally get to programming REAL patterns!